Staging: batman-adv: remove obsolete variables

This patch removes a variable that became obsolete since the skb handling
replaced the packet handling thread.

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>